Optics: measuring and testing – For light transmission or absorption
Reexamination Certificate
1999-07-26
2001-05-01
Font, Frank G. (Department: 2877)
Optics: measuring and testing
For light transmission or absorption
C600S319000
Reexamination Certificate
active
06226089
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of and a system for measuring the glucose concentration in an organism, and more particularly to a method of and a system for noninvasively measuring the glucose concentration in aqueous humor in an anterior chamber.
2. Description of the Related Art
Though the mean level of the glucose concentration in the blood varies from person to person, it is an important indication on the basis of which whether a diabetic is to be dosed is determined.
The blood glucose concentration largely varies in a very short time according to the kind of meal and/or physical activities or due to concurrence of diseases. An emergency dosing is often required due to abrupt increase of the blood glucose concentration.
Accordingly, it is desired that the blood glucose concentration of the patient be monitored at as short intervals as possible. Conventionally, the blood glucose concentration has been generally monitored by cutting the tip of a finger of the patient and analyzing the blood thus collected. Accordingly because of pain accompanying cutting the finger, it is difficult to force the patient to be subjected to measurement of the blood glucose concentration a plurality of times a day.
Recently there have been proposed noninvasive methods of measuring the blood glucose concentration instead of an invasive method having such drawback.
The noninvasive methods mainly involve noninvasive measurement of the glucose concentration in aqueous humor in the anterior chamber between the cornea and the lens of the human eyeball. The glucose concentration in aqueous humor in the anterior chamber has a close relation with the blood glucose concentration though the relation varies from person to person.
In one of such noninvasive methods, the glucose concentration is determined on the basis of optical rotation of infrared rays entering the aqueous humor in an anterior chamber as disclosed, for instance, in Japanese Unexamined Patent Publication No. 51(1976)-75498 (corresponding to U.S. Pat. No. 3,958,560). In another method, Raman scattering light by glucose is measured as disclosed, for instance, in PCT Japanese Publication No. 6(1994)-503245. In still another method, optical properties of light reflected by the lens is measured as disclosed, for instance, in Japanese Unexamined Patent Publication No. 6(1994)-237898.
We have proposed a noninvasive method of measuring the glucose concentration in aqueous humor in an anterior chamber in Japanese Unexamined Patent Publication No. 9(1997)-299333 in which a plurality of laser beams or the like different in wavelength band are caused to enter the eyeball, intensity of backscattering light from an interface between the cornea and the aqueous humor in the anterior chamber and intensity of backscattering light from an interface between the aqueous humor in the anterior chamber and the lens are accurately detected by wavelength band, for instance, by light heterodyne measurement, absorption properties of the aqueous humor for the respective wavelength bands are obtained on the basis of the backscattering light intensities and the like and the glucose concentration in the aqueous humor is obtained by near-infrared spectrometry including multivariate analysis on the basis of the absorption properties of the aqueous humor for the respective wavelength bands. Further we have proposed a noninvasive method of measuring the glucose concentration in aqueous humor in an anterior chamber in Japanese Patent Application No. 9(1997)-358101 in which the glucose concentration in the aqueous humor is determined on the basis of the refractive index of the aqueous humor in the anterior chamber which is determined on the basis of intensity or the like of reflected light from the anterior chamber, the refractive index of the aqueous humor in the anterior chamber having a very close relation with the glucose concentration in the aqueous humor.
In the systems where light is caused to enter the eyeball, it is necessary to suppress influence of the light on the eyeball as low as possible, and especially in the case where the light is a laser beam, the intensity of the laser beam must be carefully controlled.
However, in any of the above identified patent publications, there is no disclosure on a means for controlling the intensity of the laser beam to be entered in the eyeball.
SUMMARY OF THE INVENTION
In view of the foregoing observations and description, the primary object of the present invention is to provide a method of and a system for measuring the glucose concentration in aqueous humor in an anterior chamber in which the intensity of a laser beam to be entered in the eyeball can be properly controlled.
In accordance with a first aspect of the present invention, there is provided a method of measuring the glucose concentration in aqueous humor in an anterior chamber comprising the steps of detecting the intensities of backscattering light generated by predetermined interfaces of an eyeball when a laser beam emitted from a semiconductor laser is projected onto the eyeball in a predetermined position, determining the absorbance or refractive index of the aqueous humor in the anterior chamber of the eyeball on the basis of the intensities of the backscattering light, and determining the glucose concentration in the aqueous humor on the basis of the absorbance or refractive index of the aqueous humor in the anterior chamber thus determined,
wherein the improvement comprises the steps of
disposing an extinction filter on the optical path of the laser beam between the semiconductor laser and the eyeball so that the intensity of the laser beam entering the eyeball is reduced not higher than a predetermined value of MPE.
The MPE is a maximum permissible exposure (JIS C 6801, 6802) defined in JIS (Japanese Industrial Standard) and applied to exposure of the eyeball to a laser beam.
The predetermined value of MPE is obtained on the basis of the following tables 1 and 2 which are an extract of JIS C 6802 “Table 2, MPE values for eyes watching a divergent light source”. For example, when the eyeball is to be exposed using the optical system shown in
FIG. 10
to a laser beam of a wavelength of 700 nm to 1050 nm for one second with a solid angle of 3.5×10
−4
and a beam size of 0.038 mm
−2
at the surface of the eyeball, the predetermined value of MPE is 10 &mgr;W, and when the eyeball is to be exposed using the optical system shown in
FIG. 10
to a laser beam of a wavelength of 1050 nm to 1400 nm for one second with a solid angle of 3.5×10
−4
and a beam size of 0.038 mm
−2
at the surface of the eyeball, the predetermined value of MPE is 40 &mgr;W.
TABLE 1
wavelength[nm]
exposure time 10
−8
to 10 [seconds]
700 to 1050
10
5
× 10
{(&lgr;−700)/500}
× t
0.33
[Jm
−2
sr
−1
]
1050 to 1400
5 × 10
5
× t
0.33
[Jm
−2
sr
−1
]
TABLE 2
wavelength[nm]
exposure time 10
3
to 3 × 10
4
[seconds]
700 to 1050
6.4 × 10
3
× 10
{(&lgr;−700)/500}
[Wm
−2
sr
−1
]
1050 to 1400
3.2 × 10
4
[Wm
−2
sr
−1
]
As the correlation of the refractive index of aqueous humor in an anterior chamber and the glucose concentration therein, for instance, that shown in
FIG. 6
may be employed. The correlation shown in
FIG. 6
can be typically expressed by the following regression equation (correlation coefficient:0.9516).
n
2
=1.33322+1.6×10
−6
×G
wherein G represents the glucose concentration (mg/dl).
For example, the semiconductor laser may radiate a laser beam in a visible region or a near-infrared region at an intensity of several mW (1 to 9 mW, e.g., 3 to 4 mW) and a ND filter whose optical density is in the range of 3 to 4 inclusive may be employed as the extinction filter.
The absorbance of the aqueous humor in the anterior chamber of the eyeball is determined o
Font Frank G.
Fuji Photo Film Co. Ltd
Natividad Phil
Sughrue Mion Zinn Macpeak & Seas, PLLC
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